Summary: chapter 13
Client/Server Computing is replacing both main-frame-dominated: *centralized computing approaches · alternative forms of distributed data processing table 13.1 client/server environment composed by: · client: single-user PC or workstation. User friendly interface · server: provide a set of shared user services to the clients. Ex: database server. · Network: users, applications, and resources are distributed by a LAN or WAN. Characteristics that make client/server distinct: *jl * · User has greater choice in selecting products and in mixing equipment · Network management and security have a high priority in organizing and operating information systems. Client/Server Applications The platforms and the operating systems of client and server may differ. The communications software enables client and server to interoperate. Ex: TCP/IP. The success of a client/server environment depend on the design of the user interact to the client machine. Fig 13.2 Database Applications The server is essencially a database server. Client makes a database request and receives a database reponse. Server is responsible for maintaining the database Applications that make use of the database can be housed on client machines Software enables the client to make requests for access to the server’s database. Fig 13.3 13.4 Classes of Client/Server Applications The work between client and server can be divided differently · Host-based processing: - traditional mainframe environment: processing done on a central host. - User interface is via a dumb terminal. · Server-based processing: - client provide user-friendly interface - all the processing is done on the server. · Client-based processing: - application processing is done at the client - data validation routines and database functions are performed at the server. · Cooperative processing: - application processing is performed taking advantage of the strengths of client and server. Three-Tier Client/Server Architecture Application software is distributed among three typos of machines: - User machine: client machine (thin client). - Middle-tier server: *gateways between thin user clients and a variety of backend database servers.